title: Experimentally induced deep cervical muscle pain distorts head on trunk orientation.
abstract: OBJECTIVE
  We wanted to explore the specific proprioceptive effect of cervical pain on sensorimotor control. Sensorimotor control comprises proprioceptive feedback, central integration and subsequent muscular response. Pain might be one cause of previously reported disturbances in joint kinematics, head on trunk orientation and postural control. However, the causal relationship between the impact of cervical pain on proprioception and thus on sensorimotor control has to be established.
  
  
  METHODS
  Eleven healthy subjects were examined in their ability to reproduce two different head on trunk targets, neutral head position (NHP) and 30° target position, with a 3D motion analyser before, directly after and 15 min after experimentally induced neck pain. Pain was induced by hypertonic saline infusion at C2/3 level in the splenius capitis muscle on one side (referred to as "injected side").
  
  
  RESULTS
  All subjects experienced temporary pain and the head repositioning error increased significantly during head repositioning to the 30° target to the injected side (p = 0.011). A post hoc analysis showed that pain interfered with proprioception to the injected side during acute pain (p < 0.001), but also when the pain had waned (p = 0.002). Accuracy decreased immediately after pain induction for the 30° target position to the side where pain was induced (3.3 → 5.3°, p = 0.033), but not to the contralateral side (4.9 → 4.1°, p = 0.657). There was no significant impact of pain on accuracy for NHP. A sensory mismatch appeared in some subjects, who experienced dizziness.
  
  
  CONCLUSIONS
  Acute cervical pain distorts sensorimotor control with side-specific changes, but also has more complex effects that appear when pain has waned.
authors.affiliation: Unit for Specialized Pain Rehabilitation, Department of Rehabilitation Medicine, Skåne University Hospital, 221 85, Lund, Sweden, eva-maj.malmstrom@med.lu.se.
authors.forename: Eva-Maj
authors.initials: EM
authors.lastname: Malmström
authors.affiliation: Unit for Specialized Pain Rehabilitation, Department of Rehabilitation Medicine, Skåne University Hospital, 221 85, Lund, Sweden, eva-maj.malmstrom@med.lu.se.
authors.forename: Malmström
authors.initials: M
authors.lastname: Eva-Maj
authors.forename: Hans
authors.initials: H
authors.lastname: Westergren
authors.forename: Westergren
authors.initials: W
authors.lastname: Hans
authors.forename: Per-Anders
authors.initials: PA
authors.lastname: Fransson
authors.forename: Fransson
authors.initials: F
authors.lastname: Per-Anders
authors.forename: Mikael
authors.initials: M
authors.lastname: Karlberg
authors.forename: Karlberg
authors.initials: K
authors.lastname: Mikael
authors.forename: Måns
authors.initials: M
authors.lastname: Magnusson
authors.forename: Magnusson
authors.initials: M
authors.lastname: Måns
mesh_terms: D000328:Adult; D005260:Female; D019416:Head Movements; D006801:Humans; D008297:Male; D063806:Myalgia / Q000503:physiopathology*; D019547:Neck Pain / Q000503:physiopathology*; D011434:Proprioception